Vibration at high speed under load/acceleration

[fishtank Junior Member Find all posts View Profile Close fishtank]

Hi all,
I have started to notice a vibration when driving over 80-90km/h. I notice that it is most noticeable when the engine is under load. Ie going up hills. It also seems to pulsate when driving on the flat so it seems to only happen when under load. Driving or rolling fast down hills does not cause the vibration.
I am ruling out wheel bearings at this stage. Sounds like a transmission/engine/drive train thing. Only bought the car 6 months ago so not real sure on history other than a friends promise that it had regular servicing. Transmission fluid looks OK not dark or black or anything.
Any known issues/problems for this sort of thing?
Its a 1998 3.4 petrol auto with 370,000 kms.
Thanks!

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Check the 2x engine and 1x transmission mounts. You'll need an assistant to apply constant pressure to the brakes whilst simultaneously accelerating on/off a little whilst in gear/running. Chock wheels as well if you wish. During this you have peek underneath and in engine bay to sight excessive movement. Do not engage low range for this test.

By transfer design most power is sent to the rear, so another possibility is rear drive train including rear wheels/tyres. Try moving both rears tyres to front and vise versa for a test. Try removing rear prop shaft, engage transfer lock, and test.

[Leethal Advanced Member Find all posts View Profile Close Leethal]

Check your universals as well, pulsating on level roads can be caused by a binding universal joint.

[fishtank Junior Member Find all posts View Profile Close fishtank]

Thanks a lot guys for those replies however my mechanical experience is limited I have done some research and those things seem a bit out of my league to check myself but I will mention them when I take the vehicle in for a check over.

Is there anything else I could possibly check myself? Perhaps rear diff fluid could a low level or old diff fluid cause something like this?

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

It's quite easy to rotate tyres, just a little bit of a nuisance without professional lifting tools. This will help indicate if it's related to tyre balance.

The rear prop shaft is only held in place there by 8 nut/bolts, so removing it is also quite easy - although they tend to get stuck at the transfer side so some penetrating fluid and a brass hammer is often needed to shock them apart. This will help indicate if the rear prop shaft, diff or axle is the issue.

If those tasks are too daunting for you then you won't be solving the vibration issue yourself. Vibrations are always difficult to solve and sometimes an endless pursuit. Many mechanics will just start guessing and changing parts at your expense until the right one is found (or you stop going back).

[crembz Lurker Find all posts View Profile Close crembz]

I have the same problem with mine at 250000ks. At first I thought tyre related (flat spot or failed sidewall) or balance, but as soon as I lift the accelerator and remove engine load the vibration vanishes. Also no vibration down hill. Op, did you find the cause?

[crembz Lurker Find all posts View Profile Close crembz]

OK so any advice on this one. I've done a ton of reading and seems to be a recurring issue on these Prado's and even the 120s. Doesn't seem to be a consensus and some have spent heaps trying to resolve. Could be anything in the driveline if it's not engine or exhaust related.

From my diagnosis I think it's worn u-joints. Can't replicate the vibration or accompanying noise in the drive way, neutral or in drive, which means it must be shafts or wheel/tyre related. The vibration is not consistent with speed or road surface which rules put tyres. Disappears as soon as the driveline is coasting, reappears at the same rpm if the engine is loaded slightly say a slight hill. Vibration vanishes if you drop a gear (increase rpm). Can be felt regardless of gear at around 2100 rpm but is worst at freeway speed which suggests it's not the transmission, xfer case or diffs. Being inconsistent with speed also rules out wheel bearings and swerving makes no difference.

At low speed (50-80) the vibration is still present in the same situation, 1.9k - 2.2k rpm with slightly loaded driveline, but it's very difficult to detect.

My next step is to remove the front and then the rear props systematically, and driving the vehicle as a fwd and then rwd. This should help test the diagnosis and isolate the problem.

I've read people remove the front and drive rwd. Is it safe to do the same but drive fwd given the weight of the vehicle?

[6834cc Lurker Find all posts View Profile Close 6834cc]

I seem to have exact same problem. 2007 V6 with 260k on it. I can feel it at any speed, and as soon as I'm off the accelerator, there is zero vibration. Going around a slight bend whilst giving it a bit seems to make it even more evident. I'm beginning to think it's the unis as well.

[crembz Lurker Find all posts View Profile Close crembz]

I seem to have exact same problem. 2007 V6 with 260k on it. I can feel it at any speed, and as soon as I'm off the accelerator, there is zero vibration. Going around a slight bend whilst giving it a bit seems to make it even more evident. I'm beginning to think it's the unis as well.

Hey mate, still trying to with things out. I had both shafts checked and the rear rebuilt (which created an all new vibration) on declaration. Mine isn't a vibration, more of a thumping, like a jackhammer, about 5-6 thuds per second. I just has a used gearbox, xfer case and torque converter installed due to an unrelated issue. This has helped clear up a few vibrations but that thudding is still there. I've also noticed a wheel bearing type sound becoming more prominent, perhaps this is a bearing problem?

[Black 150 Member Find all posts View Profile Close Black 150]

I had vibration mainly noticeable under acceleration/load.I never mentioned it to #### when he serviced it because I didn't think much of it, however when on the hoist he advised my left front drive/cv axle was buggered as it was clunking when the tyre rotated by hand.

I got a new shaft for $175 and fitted it myself and not the vibration is fixed.

Mines a 150 series